I would not, I may consider it if I had family in there, but it is a good way of getting myself killed along with more people. I do not have training to do much of anything. Me going in, armed or not, is pretty much expecting a lucky break or shot to save the day.
The probability of that, with fear, is pretty low. I would rather call the police and let them deal with it.
The only way I could see me doing or attempting much of anything was if I was already there, was trapped (alone or more likely with others) and the person was trying to get in. At that point, it is do or die and what do you have to lose?
Other than that, I am not going to try and be an action hero. Even if I am in that situation I am running or hiding. I would like to think I try to help some others get out if it is safe for us to go but that is probably the extent of my heroism.
I have found the trend of some, to blame the male students for not attacking the guy to be sad. It is coming from a hyper macho crowd and is sexist in its own way. Just because one is male does not grant you super powers and the ability to overcome fear at will. Some people have more of that drive than others, but there were many acts of heroics there. And those people showed more humanity than the clowns spouting off. People should be ashamed of themselves and their views of these things.
By the time that they got there, it would be too late. Cops SOLVE and avenge crimes and murders, they don't STOP them. It would most likely be minutes before the cops or Swat teams got there.